Disclosed is a method of fabricating a multi-layered PCB, in which the optical waveguide component is inserted into the PCB in such a way that a prepreg adhesive does not block an optical signal entrance of the optical waveguide. The method comprises pre-routing a portion of an adhesive meeting the optical waveguide to remove said portion, processing an adhesive weeping prevention layer so as to prevent the adhesive from blocking the optical signal entrance of the optical waveguide, arranging the optical waveguide, the adhesive, and the adhesive weeping prevention layer on a copper clad laminate, and combining the optical waveguide, a prepreg, and the adhesive weeping prevention layer with each other into a single structure. The adhesive weeping prevention layer is selected from the group consisting of a prepreg, a single-sided copper clad laminate, a thermally curable resin, a heat spreader, and an unclad. Therefore, the method is advantageous in that the prepreg and the adhesive weeping prevention layer are pre-routed to prevent epoxy resin from blocking the optical signal entrance of the optical waveguide, thereby facilitating precise interfacing of optical signals.